US3826913A

US3826913A - Distributively banded reflector surface for producing contoured illumination intensity

Info

Publication number: US3826913A
Application number: US00363509A
Authority: US
Inventors: R Downing; E Wiley
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1973-05-24
Filing date: 1973-05-24
Publication date: 1974-07-30
Anticipated expiration: 1991-07-30

Abstract

A concave light reflector is shaped to have flat-sectioned radial bands on its inner surface extending radially outwardly and forwardly from the apex of the reflector. The bands are distributed circumferentially in an asymmetrical manner to provide a desired cross-sectional contour of illumination intensity, such as approximately rectangular for photographic projection purposes.

Description

United States Patent [191 Downing et al.

[111 3,826,913 [451 Jul '30, 1974 DISTRIBUTIVELY BANDED REFLECTOR SURFACE FOR PRODUCING CONTOURED ILLUMINATION INTENSITY Inventors: Robert D. Downing, Mentor;

Emmett H. Wiley, Chesterland, both of Ohio General Electric Company, Schenectady, N.Y.

Filed: May 24, 1973 Appl. No.: 363,509

Assignee:

US. Cl. 240/103 R, 240/4l.36

Int. Cl. F21v 7/09 Field of Search 240/l05, 41.36, 103 R, 240/ 103 C References Cited UNITED STATES PATENTS Balsillie IMO/41.36

Primary Examiner-Samuel S. Matthews Assistant Examiner-Russell E. Adams, Jr.

Attorney, Agent, or Firm-Norman C. Fulmer; Lawrence R. Kernpton; Frank L. Neuhauser ABSTRACT A concave light reflector is shaped to have flatsectioned radial bands on its inner surface extending radially outwardly and forwardly from the apex of the reflector. The bands are distributed circumferentially in an asymmetrical manner to provide a desired crosssectional contour of illumination intensity, such as approximately rectangular for photographic projection I purposes.

9 Claims, 3 Drawing Figures DISTRIBUTIVELY BANDED REFLECTOR SURFACE FOR PRODUCING CONTOUREI) ILLUMINATION INTENSITY BACKGROUND OF THE INVENTION The invention is in the field of lighting devices, par ticularly the type having a concave reflector for directing illumination in a given direction.

Concave reflectors have been made in parabolic and ellipticalconfigurations, and combinations and modifications of these and other configurations, to produce desired patterns of projected light, such as a diverging light beam for broad-area illumination purposes or a converging light beam for photographic projection purposes such as in projectors for movies or slide transparencies. Usually a small light source of high intensity is positioned at the focal point of the reflector.

A typical concave reflector of circular cross section will project a light beam having circular contours of equal light intensity. However, a rectangular type of equal light intensity contour is desired for certain purposes, such as in diverging-beamphotographic lamps for illuminating a scene to be photographed and in converging-beam projection lamps for movie and slide projectors, Various ways have been devised for shaping a concave reflector surface to produce a substantially rectangular or oval light intensity configuration. For example,'U.S. Pat. No. 3,331,960 to Elmer describes a concave reflector having a non-circular cross section; US. Pat. No. 3,423,582 to Elmer describes a concave reflector having four parabolic quadrants each with a different axis; U.S. Pat. No. 3,428,800 to Levin-and Lemons describes a concave reflector having a contoured front edge; US. Pat. No. 3,588,493 to Nordquist describes a concave reflector having four specially shaped sections or quadrants; and US. Pat. No. 3,720,460 to Wilkinson describes a concave reflector oriented to provide an offset angle of the focus axis.

SUMMARY OF THE INVENTION Objects of the invention are to provide a new and improved concave reflector for projecting a beam of light having a substantially rectangular or oval crosssectional configuration of light intensity,.and todo so with a reflector having a substantially circular cross section.

The invention comprises, briefly and in a preferred embodiment, a concave light reflector which may have a generally circular cross-sectional shape, the inner surface thereof being shaped to provide a plurality of radial bands extending radially outwardly and forwardly from the apex of the reflector. The bands are distrib- FIG. 2 is a front view of the assembly of FIG. 1; and

FIG. 3 is a front view of an alternative embodiment of the invention.

DESCRIPTION OF THE PREFERRED. EMBODIMENT The general type of lamp and reflector assembly shown in the drawing is described in detail in US. Pat. No. 3,700,881 to Stanley Slomski, and comprises a concave reflector ll of molded glass provided with a multiple layer dichroic light-reflective coating 12 on the inner surface thereof. The cross section of the reflector is circular. A compact high intensity lamp 13 is positioned within the reflector 11, and preferably com prises an elongated quartz envelope having a bulbous portion intermediate the ends thereof in which a high intensity are discharge is located at the focus of the reflector 11. A ceramic end cap 14 is attached to the rear of the reflector l1, and a pair of electrical connection wires l6, 17 extend from the end cap 14 and are attached to a connector plug 18. One of the connector wires 16 is connected to an electrode (not shown) at the rear end of the lamp 13,'and the other connector wire 17 is connected to a lead-in wire at the front end of the lamp 13, via an insulated connecting wire l9. A ceramic protective disc 20 is attached over the front lead-in of the lamp. v

In accordance with the invention, a plurality of radial bands 21 are formed on the inner surface of the reflector 11, extending radially outwardly and forwardly from the apex of the reflector, and distributed circumferentially in an asymmetrical manner. Each-of the radial bands 21 tapers to a point lying on acircumference rearwardly spaced from the front edge of the reflector 11. The radial bands 21 may be made by molding them simultaneously with molding the reflector, by suitably shaping the reflector die or mold. The cross-section of each band, in planes perpendicular to the optical axis of the reflector, preferably is substantially flat, but may be inwardly curved toward the optical axis, or outwardly curved away from the optical axis with a radius uted circumferentially in an asymmetrical manner to provide a desired cross-sectional contour of illumination intensity. A substantially rectangular or ovallight intensity contour is obtained by providing a certain number of radial bands on each of a pair of opposed quadrants of the surface of the reflector, and a lesser number of wider radial bands on each of the other pair of opposed quadrants. In a modification, radial bands are provided on only one pair of opposed quadrants of the reflector surface.

BRIEF DESCRIPTION'OF THE DRAWING FIG. 1 is a perspective view of a lamp and reflector assembly in accordance with a preferred embodiment of the invention;

of curvature different from that of the circular main body of the reflector.

In the embodiment of FIGS. 1 and 2, the radial bands 21 at the side quadrants of the reflector are relatively more numerous and narrower than the radial bands 21 at the top and bottom quadrants of the reflector. This asymmetrical arrangement of the radial banding produces a substantially rectangular or oval light intensity contour having a longer dimension horizontally than vertically, as indicated by the dashed-line representative light intensity contour curve 22 in FIG. 2. By suitably shaping the axial curvature of the reflector 11, the reflector will project forwardly a light beam from the lamp 13, of either a diverging or converging shape. The light intensity contour 22, on the scale shown, is representative of the light distribution pattern of a diverging light beam at a lateral plane forwardly of the front edge of the reflector 11. For a reflector shaped to form a converging light beam, the actual size of the light intensity contour curve 22 would be smaller than the front surface area of the reflector 11; such a light intensity contour for a converging light beam is not shown in FIG. 2 since it would tend to obfuscate the structural showing.

The substantially rectangular light beam pattern, as represented by contour 22 in FIG. 2, provides a suitable light beam configuration for use in illuminating a scene to be photographed, or for illumination of documents in a document copying apparatus, in the case of a reflector 11 producing a diverging light beam; and produces a suitably shaped light beam pattern in the case of a converging light beam reflector, for suitably filling the aperture in a projector at which a movie film or slide transparency is positioned. The foregoing results are achieved without wasting light as would be the case of a circular light beam pattern, where certain outer portions of the light beam would be wasted.

The invention functions due to the fact that each radial band reflects a certain amount of light sideways of itself, and the relatively wider radial bands in the vertical quadrants of the reflector reflect relatively more light from the lamp l3 horizontally, than the amount of light reflected in vertical directions by the relatively narrower radial bands in the horizontal quadrants. The radial bands 21 also tend to soften the light beam, as described in the above-referenced U.S. Pat. No. 3,428,800 to Levin and Lemons.

The embodiment of FIG. 3 is the same as that of FIG. 2, except that the radial bands have been eliminated in the horizontal quadrants of the reflector 11, leaving the radial bands 21 only in the vertical reflector quadrants. The asymmetrical banding arrangement of FIG. 3 produces a light beam having a substantially rectangular or oval light intensity configuration as is shown by the line 22 in FIG. 2, this being achieved, as described above, because the vertical radial bands 21 reflect some of the light from the lamp 13 sideways in a horizontal direction.

Various other asymmetrical radial banding configurations can be employed on reflectors of various kinds. For example, if the radial bands 21 were omitted from the upper quadrant in FIG. 3, the light beam projected by the reflector l 1 would be widened horizontally only in the lower part of the projected beam, such as might be useful for automobile headlights or airplane lights. In any of the embodiments, the radial bands may extend radially with respect to the apex without reaching either the apex or the front rim, or they may extend completely from the apex to the front rim, or from the apex toward the front rim (as shown in the drawing), or from the front rim toward the apex.

While preferred embodiments of the invention have been shown and described, various other embodiments and modifications thereof will become apparent to persons skilled in the art and will fall within the scope of the invention as defined in the following claims.

What we claim as new and desire to secure by Letters Patent of the United States is:

l. A concave light reflector having a generally circular cross section and provided with radial bands on the inner surface thereof extending radially outwardly and forwardly with respect to the apex of the reflector, wherein the improvement comprises an asymmetrical arrangement of said bands with respect to a circumference of said surface, whereby said reflector will projecta non-circular beam of light from a lamp positioned therein, each of said radial bands being separated from the adjacent bands along at least a substantial portion of the lengths thereof, the reflector surface between adjacent bands being circular cross-section segments that are relatively wider at distances relatively farther from said apex of the reflector said radial bands having a cross-sectional curvature different from said separating surfaces.

2. A reflector as claimed in claim 1 in which a plurality of said radial bands are provided in each quadrant of the reflector, the radial bands in one pair of opposed quadrants being symmetrical with respect to one another and asymmetrical with respect to the radial bands in the other pair of opposed quadrants.

3. A reflector as claimed in claim 2 in which said one pair of opposed quadrants contains a different number of said radial bands than does said other pair of op posed quadrants.

4. A reflector as claimed in claim 2 in which said radial bands in said one pair of opposed quadrants are relatively wider than the radial bands in said other pair of opposed quadrants.

5. A reflector as claimed in claim 1 in which said radial bands are provided in only one pair of opposed quadrants of said reflector.

6. A reflector as claimed in claim 5 in which the ra dial bands in said pair of opposed quadrants are symmetrical with respect to one another.

7. A reflector as claimed in claim 1 in which the surface of each of said radial bands is substantially flat in a plane perpendicular to the optical axis of said reflector.

8. A reflector as claimed in claim 1, contoured to have a focus point within the reflector, and in which each of said radial bands tapers toward a point in a direction toward the front edge of said reflector surface.

9. A reflector as claimed in claim 1 in which said radial bands are located in at least one of the quadrants of said reflector.

Claims

1. A concave light reflector having a generally circular cross section and provided with radial bands on the inner surface thereof extending radially outwardly and forwardly with respect to the apex of the reflector, wherein the improvement comprises an asymmetrical arrangement of said bands with respect to a circumference of said surface, whereby said reflector will project a non-circular beam of light from a lamp positioned therein, each of said radial bands being separated from the adjacent bands along at least a substantial portion of the lengths thereof, the reflector surface between adjacent bands being circular cross-section segments that are relatively wider at distances relatively farther from said apex of the reflector said radial bands having a cross-sectional curvature different from said separating surfaces.

3. A reflector as claimed in claim 2 in which said one pair of opposed quadrants contains a different number of said radial bands than does said other pair of opposed quadrants.

6. A reflector as claimed in claim 5 in which the radial bands in said pair of opposed quadrants are symmetrical with respect to one another.